Field of the Invention
The present invention relates to an information processing system including a communication device and a storage device.
Description of the Background Art
An information processing system including a communication device and a semiconductor memory connected to each other employs a technique to mutually authenticate validity between the communication device and the semiconductor memory (mutual authentication technique) before allowing an access to content data, in order to prevent fraudulent reading of content data stored in the semiconductor memory.
In general challenge-response mutual authentication, the communication device generates a first authentication code, and encrypts and sends the first authentication code to the semiconductor memory. The semiconductor memory decrypts the received first authentication code, and encrypts the first authentication code again and sends back to the communication device. The communication device decrypts the received first authentication code, and checks for agreement between the first authentication code sent to the semiconductor memory and the first authentication code received from the semiconductor memory, in order to authenticate validity of the semiconductor memory. After authentication of the validity of the semiconductor memory by the communication device, the semiconductor memory generates a second authentication code, and encrypts and sends the second authentication code to the communication device. The communication device decrypts the received second authentication code, and encrypts the second authentication code again and sends back to the semiconductor memory. The semiconductor memory decrypts the received second authentication code, and checks for agreement between the second authentication code sent to the communication device and the second authentication code received from the communication device, in order to authenticate validity of the communication device.
JP2000-349751A describes an information processing device in which multiple mutual authentication procedures are prepared in advance, and a CPU selects one of the mutual authentication procedures and perform the selected mutual authentication procedure.
According to the above-described general challenge-response mutual authentication, sending of the first authentication code from the communication device to the semiconductor memory and receiving of the response value, and sending of the second authentication code from the semiconductor memory to the communication device and receiving of the response value are performed sequentially. Thus time required for mutual authentication is prolonged, and the processes are complicated.
Mutual authentication between the communication device and the semiconductor memory is generally performed by software processing in which a microprocessor performs an authentication program. Thus an attacker who intends to read content data in a fraudulent way would analyze authentication programs or tamper with data of a ROM or RAM in the microprocessor, so as to manipulate control of the microprocessor to avoid mutual authentication. Such manipulation will allow fraudulent reading of content data from the semiconductor memory.